In many countries, because of relatively stringent requirements for exhaust gas composition, lambda regulation in internal combustion engines of motor vehicles is already standard equipment. The lambda regulation functions with an exhaust gas sensor which switches over, that, is changes between limiting values at a mixture where lambda=1; for example, each time the sensor voltage goes through a zero value, the integration direction of the integrating controller changes, which causes lambda to be always controlled in the direction of .lambda.=1. In order to obtain these switching processes, the mixture is continuously enriched and leaned down again. Since necessarily there is a period of time before the sensor reacts to a change in mixture composition, undesirable peaks in exhaust gas values are continuously produced. If a slight enrichment is selected, then it may under some circumstances take a while until the next switchover point has again been attained. In the opposite instance, that is, if heavy enrichment is provided, then because of the transit time "overswings" or oscillations of the mixture and exhaust gas occur, thus producing such exhaust gas peaks.
A lambda regulation device disclosed in U.S. Pat. No. 3,782,347 detects the period of time between two switchover processes and after a predetermined interval of time has elapsed in which no switchover process occurs, then a switchover is made to a different, shorter time constant in the regulating amplifier. As a consequence of this, an amplified change in the mixture occurs after this predetermined period of time has elapsed, which in turn causes a more rapid switching process. However, the danger then exists of a certain degree of overcontrol, producing undesirable exhaust gas emissions.
Although this known regulating device is generally capable of producing satisfactory results, still it does not attain an optimum in terms of clean exhaust gas, because of the exhaust gas peaks which necessarily occur.